The basic objectives of the study are: (a) To formulate the simplest mathematical description of the head and spine consistent with explaining the clinical observations on traumatic injury to these parts of the human body. The mathematical models completed thus far include material-filled spherical shells to simulate head injury and chains of wedges to represent the layered-medium construction of the spine. (b) To perform the necessary experimental studies to obtain the biomechanical data needed to implement the mathematical models developed. These have included the distribution of segmental inertial properties of the human trunk and the material properties and failure criterion of the intervertebral joints under complex loading. The in vivo dynamic material properties of the spinal cord are being determined from its wave transmission characteristics. (c) To construct a mechanical model of the head to simulate the measurement of intracranial pressure distribution as a prelude to in vivo measurement of primates. (d) To develop hybrid computer optimization techniques for the synthesis of head protection devices. So far, the case of linear lumped- parameter elements without space limitations has been completed. Current work in progress includes optimization of nonlinear lumped-parameter elements within a given space interval.